A method of synthesizing a biocompatible hydrogel by covalently cross-linking an effective amount of a first macromonomer including a cyclic thioester group with an effective amount of a second macromonomer including a terminal cysteine group is disclosed. The trimmer mechanism allows for a linearly reciprocating motion to be used to obtain a close trim or shave. The low-pressure drive gear is supported in the intermediate casing by an axial-positioning bearing. The fastening means simultaneously applies deforming forces to the peripheries of the plates to create a continuous spring force to effect electrical continuity between the integrated circuit package and the circuit board.